This popped up on my reddit, and I found it an interesting read:
One of the most successful coups the British Special Operations Executive pulled off during WWII was actually against the Italians.
In early 1941, a seemingly small idea was put forth as a way to interfere with the Italian Army in North Africa, and damage coordination between the Italians and the Germans. The idea posed little risk, and seemed easy enough to pull off, so it was quickly approved. No one could have known how successful it would be. The basic idea was to create a German-Italian military phrase dictionary with subtle errors inserted, print hundreds of them on Italian paper stock from before the war with artificially aged inks, and covertly slip them into the Italian supply chain in North Africa.
